Preparation of polymethyladamantanes



1- I I A. SCHNEIDEIIQ ETAL 3,336,406

PREPARATION OF POLYMETHYLADAMANTANES I Filed Sp L 10, 1965 5 heets-Sheet1 FIG. I

. T EX-OVTHE'RM FOR INITIALSTAGE 0F PERHYDROACENAPHTHENE ISOMERIZATIONHEATING MEDIUM CARBON I 20 40 so so Too, 'TIME, MINUTES I NVENTORSABRAHAM SCHNEIDER EDWARD .1. JANOSKI B ROY w; MC GINNIS' QQMW.

ATTORNEY Aug. 15,1967

v A; SCHNEIDER ETAL PREPARATION OF POLYMETHYLADAMANTANES Filed Sept.-10, 1965 3 heets-Sheet 2 $52.2 d2 2954mm ooN v GI 02 iii/53019 55 mezofifi wzoww.

.LOHOOHd NOGHVOOHGAH NI /o 1M INVENTORS ABRAHAM SCHNEIDER EDWARD J.JANOSKI BY ROY w. MC emms ATTORNEY 3 heets-Sheet 3 ,3- DlMETHYL-A YAl-SCHNEIDER E AL PREPARATION OF POLYMETHYLAQAMANT-ANES 1 FORMATION OF IFROM PERHYDROACENAPTHENE Filedse 'pt 10 1-965v E3035 zomm omer z 0 tsMINUTES 40 so REACTION TIME",

United States Patent 3 336 406 PREPARATION OF POLYMETHYLADAMANTANESAbraham Schneider, Overhrook Hills, and Edward J.

Janoski, Havertown, Pa., and Roy W. McGinnis, Wil- 3,336,406 PatentedAug. 15, 1967 less the catalyst does not cause an inordinate amount ofcracking to occur. Hence a high yield of the desired ultimateisomerization product can be obtained in relatively short reactiontimes.

In practicing the present invention any perhydroaror fif gi fi gf g3523122 3 fi s g gg g Plum 5 matic hydrocarbon which has three rings andfrom twelve Filed Sept. 10, 1965, Ser. No. 486,307 to fourteen carbonatoms lHClllSlV8 can be used. A table 16 Claims. (Cl. 260-666) ofnumerous tricyclic aromatics which can be hydrogenated to producecorresponding C C perhydrocar- This invention relates to the catalyticisomerization of bons is presented in the aforesaid patent. Any suchper- C -C tricyclic perhydroaromatic hydrocarbons to prohydroaromatichydrocarbon will readily isomerize under duce polymethyladamantanes.More particularly the inthe conditions herein specified to form aproduct having vention concerns the conversion of such perhydroaromatican adamantane nucleus and methyl substituents located hydrocarbons intoadamantanes having the same number at bridgehead positions. Since thenucleus has ten carbon of carbon atoms and from two to four methylgroups at- 15 atoms, the product will have from two to four carbontached to bridgehead carbon atoms of the adamantane atoms in excess ofthose required for forming the nucleus, nucleus. Specific bridgeheadpolymethyladamantanes predepending upon the particular perhydroaromaticselected pared according to the invention are the following: 1,3- asstarting material. These excess carbon atoms will alldimethyladamantane; 1,3,5 trimethyladamantane; and appear as methylgroups located at bridgehead positions 1,3,5,7-tetramethyladamantane. inthe final isomerization product.

The conversion of tricyclic perhydroaromatic hydro- In the transitionfrom the starting material to the polycarbons of twelve or more carbonatoms to isomers having methyladamantane product it has been found thatthe an adamantane nucleus has been described in United isomerizationpath for tricyclic perhydroaromatics leads States Patent No. 3,128,316.As disclosed in the patent through an intermediate stage at which anethyl group is this isomerization is effected at a temperature in therange attached to the adamantane nucleus at both brid ehead of 5 C. to50 C. by means of an aluminum chloride and non-bridgehead positions.This is illustrated for the or bromide catalyst. The hydrocarbons gothrough vari- C perhydroaromatic, acenaphthene, by the following ousconversion stages; but if the isomerization reaction is equation:

C-C n n PERHYDRJ- l-ETHYL- Q-E'I'HYL- AC ENF. PHTHENE! ADAMANTANEADAMANTAN E carried to completion, the ultimate product is mainly apolymethyladamantane having two or more methyl groups attached tobridgehead carbon atoms of the a-damantane nucleus. However, under theconditions taught in the patent the isomerization reaction proceedsslowly and an undesirably long reaction time is required to attain themaximum yield of the bridgehead polymethyl isomers. Merely raising thereaction temperature to above the 50 C. maximum value taught in thepatent and contacting the hydrocarbon reactant with catalyst for .a longenough time to produce mainly the bridgehead polymethyl products is notsatisfactory, as this tends to promote cracking reactions which causerapid deactivation of the catalyst. Hence, according to the patent thereaction temperature is maintained below 50 C. and a long reaction timeis employed in order to approach the maximum obtainable yield of thebridgehead polymethyladamantanes.

The present invention constitutes an improvement over the process ofUnited States Patent No. 3,128,316, whereby bridgeheadpolymethyladamantanes of the C -C range are produced from C -C tricyclicperhydroaromatics in a considerably more rapid reaction. Accordin to theinvention the tricyclic perhydroaromatic charge is contacted at atemperature in the range of 55150 0., preferably 70-120 C., and in thepresence of free HCl maintained at -a partial pressure of at least 0.1psi. with a pre-formed aluminum chloride catalyst complex. The catalystis a liquid complex previously prepared by reacting AlCl HCl andparaffin hydrocarbon having at least seven carbon atoms per molecule ashereinafter described. It has now been found that use of HCl in theisomerization zone at a partial pressure as specified allows thecatalyst to be employed at relatively high temperatures withoutappreciable loss of activity. Neverthe- Further isomerization convertsthe ethyl group to two methyl groups which preponderantly are located atbridgehead positions. Thus the major final product of the isomerizationof perhydroacenaph-thene is 1,3-dimethyladamantane. However, when theisomerization is complete, an equilibrium composition is reached atwhich the 1,3- isomer is mixed with minor amounts of its non-bridgeheadmethyl isomers. By non bri-dgehead as used herein in referring to aproduct is meant that at least one of the substituents is attached tothe adamantane nucleus at a n0nbridgehead carbon atom. There are threenon-bridgehead dimethyl isomers which will appear in minor amounts withthe 1,3-isomer at equilibrium. These are the following (DMA meaningdimethyladamantane): 1,2-DMA; antil,4-DMA; and syn-1,4-DMA. However, thetotal amount of these at equilibrium generally is less than 10%, so that1,3-DMA is by far the predominant product resulting from completeisomerization of perhydroacenaphthene. Isomers in which both methylgroups appear at nonbridgehead positions do not occur in any appreciableamount. The foregoing applies equally well when the starting hydrocarbonis some other C tricyclic perhydroaromatic, for example,perhydrohydrindacene.

When the starting material is a C perhydroaromatic, for example,perhydrofluorene, an intermediate isomerization product again is formedin which ethyl substituents are located at bridgehead and non-bridgeheadpositions. In this case the intermediate isomers also contain, inaddition to the ethyl group, a methyl group which may be attached atbridgehead or non-bridgehead positions. Further isomerization convertsthe ethyl group to two methyl groups and shifts non-bridgehead methylgroups mainly to bridgehead positions. Hence the predominant ultimateisomerization product is 1,3,5 trimethyladamantane (T MA) which occursin equilibrium with minor amounts of non-bridgehead TMA isomers.

In the case of C perhydroaromatics an analogous intermediateisomerization stage occurs in which the intermediate product contains anethyl group. The ethyl group subsequently disappears by conversion intomethyl groups and the predominant final product is l,3,5,7-tetramethy1-adamantane.

It has noW been found that isomerizations conducted in accordance withUnited States Patent No. 3,128,316 using an aluminum chloride catalystare difficult to carry beyond the intermediate stage discussed above,i.e., where an ethyl substituent is attached to the nucleus. Forexample, C perhydroaromatics will form ethyladamantane but then furtherisomerization to convert the ethyl group to bridgehead methyl groupsbecomes undesirably slow. Thus, when perhydroacenaphthene is contactedat 40 C. with a pre-formed AlCl -HCl-hydrocarbon complex, a majorportion can be converted to ethyladamantane in an hour or so. Howeverafter a 4-hour reaction time, typically 60% or more of the product isstill ethyladamantane and only a minor amount of 1,3-dimethyladamantanewill have been formed. The present invention obviates this difficulty ofgoing beyond the ethyladamantane stage. It also shortens the timerequired in the initial conversion of the charge hydrocarbon to reachthe ethyladamantane stage of isomerization.

The present process involves the use in the isomerization zone of freehydrogen chloride in combination with a catalyst which is a pre-formedliquid complex obtained by reacting AlCl HCl and paraffinic hydrocarbonas described below. The catalyst should contain suspended therein anexcess of AlCl over that which reacts to form the complex. Theisomeriation is conducted by contacting the hydrocarbon charge at atemperature of 55-150 0., preferably 70-120 0., with the catalyst whichconstitutes a separate liquid phase in the reactor. Gaseous HCl is addedto the reactor in order to maintain therein a partial pressure of HCl ofat least 0.1 pound per square inch (p.s.i) and more preferably at least1.0 p.s.i. An HCl partial pressure in the range of 1-30 p.s.i. istypical but a much higher HCl pressure, e.g., 100500 p.s.i., can beemployed without any adverse effect. These values refer to partialpressure of the HCl as measured at the tempera ture at which thereaction is conducted.

The mixture is continuously agitated to etfect initimate contact betweenthe phases. Under the above-stated conditions the isomerization reactiontakes place at an accelerated pace, proceeding to and through the ethylintermediate stage and producing the desired bridgeheadpolymethyladamantane in high concentration. Some amount of crackingoccurs during the reaction, resulting in the formation of small amountsof lower boiling products such as isobutane, isopentane and naphthenesof the C C range. Nevertheless the activity of the catalyst is notsubstantially reduced as long as free HCl at a partial pressure above0.1 p.s.i. is maintained in the reaction zone.

The use of a temperature exceeding 55 C. materially reduces the timenecessary for converting the perhydroaromatic charge to the ethylintermediate stage. It has been found that when the perhydroaromatic andthe preformed complex catalyst are contacted with each other while beingheated a rapid exothermic reaction takes place when the temperatureexceeds 55 C. The immediate product of this rapid reaction is thealkyladamantane containing an ethyl substituent. FIG. 1 of theaccompanying drawings graphically illustrates this rapid exothermicreaction. FIG. 1 is for the isomerization of perhydroacenaphthene andshows the temperatures of the hydrocarbon reactant and of the fluidheating medium as a function of time from start-up. The procedureemployed was as follows: At room temperature perhydroacenaphthene and apre-formed AlC -HCl-hydrocarbon complex catalyst were charged to areactor and gaesous HCl was admitted thereto to a pressure of about 25p.s.i.g. The reactor had a jacket through which the fluid heating mediumwas continuously circulated and also was provided with a stirrer forintimately contacting the hydrocarbon and catalyst phases. The run wasbegun by starting the stirrer and by continuously pumping the heatingmedium through the jacket while heating it in a preheater to raise thetemperature. The temperatures of the incoming heating medium and of thehydrocarbon reactant were continually measured, and the two curves ofFIG. 1 show the respective values obtained as against time.

As can be seen in FIG. 1 the temperature of the hydrocarbon reactantlags behind that of the heating medium in the initial heat-up period andfor a time increases at more or less the same rate as the heating fluidtmeperature increases. However, when the hydrocarbon temperature exceeds55 C., a strong exothermic reaction sets in, causing the hydrocarbontemperature to rise sharply above that for the heating medium. Thisreaction corresponds to the conversion of the perhydroacenaphthene tothe adamantane structure and it mainly produces ethyladamantanes. Theisomerization then slows down, as evidenced by the fact that thehydrocarbon temperature soon drops back toward that of the heatingmedium. If the reaction were stopped at this stage, as described andclaimed in our copending United States application Ser. No. 486,275,filed of even date herewith, the ethyladamantanes would constitute mostof the product. For the present purpose, however the isomerizationreaction is continued to obtain the bridgehead dimethyladamantane as themajor product. In order for this further reaction to proceed at areasonably rapid pace, it is necessary to have free HCl in the reactoras illustrated by FIG. 2 discussed hereinafter.

In preparing the catalyst AlCl is suspended in a paraffin hydrocarbon ormixture of paraflins having at least seven and preferably eight or morecarbon atoms per molecule and gaseous HCl is passed into the mixture. Itis desirable to use isoparatfins such as highly branched octanes,nonanes or decanes for this purpose but straight chain paraffins canalso be used. The reaction of the AlCl HCl and paraffin hydrocarbon canbe effected at room temperature, although the use of an elevatedtemperature such as 50100 C. generally is desirable to increase the rateof reaction. For best results at least five moles of the paraffin permole of AlCl should be employed. Under these conditions some of theparaffin evidently breaks into fragments, yielding a C fragment whichbecomes the hydrocarbon portion of the complex. As reaction between thethree catalyst components occurs the particles of AlCl in suspension inthe hydrocarbon become converted to the liquid complex. The addition ofHCl is stopped before all of the AlCl reacts so that the complex formedwill contain some AlCl particles suspended therein. Alternatively HCl isadded until all of the AlCl has reacted but some fresh AlCl is suspendedin the resutling complex before it is used as catalyst. The complex is areddish brown, somewhat viscous liquid which is a relatively stablematerial.

In carrying out the process of the invention the preformed catalystprepared as described above and the tricyclic perhydroaromatic chargeare introduced into a reaction zone and gaseous HCl is added thereto tomaintain the HCl partial pressure as above specified. The proportion ofcatalyst complex to perhydroaromatic charged is not critical but it isusually desirable to employ a weight ratio of complex to hydrocarbon ofat least 1:10. More preferably such ratio is at least 1:1 andconsiderably larger ratios, e.g., 10:1, can be used if desired. Thereactor should be provided with means for agitating the mixture so as toeffect good contact between the catalyst and hydrocarbon phases.Increases in the catalyst to hydrocarbon ratio and in the degree ofagitation tend to expedite the reaction. Contacting of the catalyst andhydrocarbon phases at 55150 C. While maintaining an HCl partial pressureas previously specified is continued until at least a major portion ofthe tricyclic perhydroaromatic has been converted to the desiredbridgehead polymethyladamantane. The contacting is then stopped and thehydrocarbon product is separated from the catalyst layer. By distillingoff the lower boiling products resulting from a minor amount of crackingthat occurs, the bridgehead polymethyladamantane can be obtained in highconcentration which typically is of the order of 85-92%.

In a further embodiment of the invention the bridgeheadpolymethyladamantanes are prepared in still higher concentrations, forexample, in a purity of 95% or better. In this embodiment the tricyclicperhydroaromatic charge is first reacted at a temperature of 55150 C.,preferably 70120 C., and under an HCl pressure, all as above described.This produces an equilibrium product of polymethyladamantanes comprisingmainly bridgehead products but also a minor but substantial amount ofnonbridgehead polymethyl isomers. The temperature is then dropped towithin the range of 050 C. and preferably below 30 C. and contacting ofthe hydrocarbon and catalyst phases is continued. This results in theformation of a new equilibrium mixture in which the proportion ofbridgehead to non-bridgehead isomers is substantially increased. Forexample, whereas such proportion typically may be about 90:10 for anequilibrium .mixture formed at 90 C., re-equilibrium of the mixture bythen contacting the catalyst and hydrocarbon phases at 25 C. typicallymay increase the bridgehead to non-bridgehead isomer ratio to 96:4.

The data shown in Table I specifically illustrates the benefit that canbe derived by this procedure of following the higher temperatureisomerization step with a further step for equilibrating at lowertemperature. Table I shows measured equilibrium values obtained for Cadamantanes for equilibration at relatively high and relatively lowtemperatures, specifically, 83 C. and 27 C., by means of the AlClcomplex catalyst.

TABLE I.-EQUILIBRIUM CONCENTRATIONS FOR C'm The tabulated data showsthat equilibration at 27 C. drops the total non-bridgehead DMA contentto about one-half of that for 83 C. The purity of the bridgehead isomeris increased from 90.9% to 95.7% for these temperature levels. The dataalso show that the amount of l-ethyladamantane, which is the mainintermediate formed in going from a C perhydroaromatic to the adamantanestructure, is negligible in the fully equilibrated product at eithertemperature level.

In practice a minor but substantial amount of cracked products will bepresent in the isomerization product, so that the actual content of thebridgehead isomer in the hydrocarbon phase will not be as high as shownin Table 1. However the cracked material can readily be removed bydistillation and the bridgehead isomer can thus be obtained in puritiesas illustrated in the table.

The following examples describe runs which illustrate the capabilitiesof the present process. Results from these runs are depicted graphicallyin FIGURES 2 and 3 of the accompanying drawings, as described below.

Example 1 An AlCl complex catalyst was prepared by reacting 40 ml. of2,2,5-trimethylhexane with 15 g. of AlCl at 65-75 C. while bubbling HClinto the mixture. After essentially all of the A101 had reacted, themixture was cooled and allowed to stratify, and the excess hydrocarbonwas decanted. The catalyst layer was washed with 30 ml. of2,2,5-trimethylhexane and then was blown at room temperature withnitrogen to remove any excess HCl.

A shaker bomb was charged with 10.5 g. of the so-prepared complex, 5.0g. of uncomplexed A101 and 11.0 g. of perhydroacenaphthene. The latterwas a mixture of four isomers produced by hydrogenating acenaphtheneemploying a Raney nickel catalyst. Without any free HCl being added thebomb was immersed in a water bath which had been heated to C. With thebath maintained at such temperature the bomb was agitated for 177minutes. Small samples of the hydrocarbon phase were taken at times of60, 117 and 177 minutes for analysis by vapor phase chromatography.After the third sampling the mixture was cooled to 0 C. and the bomb waspressured at that temperature with HCl to a pressure of 10 p.s.i.g. Thebomb was then reheated to 90 C. and was agitated to continue theisomerization. The partial pressure of HCl under these conditions wasabout 13.3 p.s.i. Samples were taken corresponding to total reaction oftimes (including the previous reaction period of 177 minutes) 237 and297. Analyses of the various samples are shown in Table II, which liststhe products in the order of increasing boiling points.

TABLE II.-ISOMERIZATION OF PERHYDROACENAPH- THENE AT 90 C. WITHOUT ANDWITH FREE 1101 Reaction time, min 60 117 177 237 297 Free H01 None NoneNone Yes Yes Composition of Product,

wt. percent:

C4 parafrins 1.6 2. 6 2. 7 2. 2 7. 4 1.4 3.1 3. 0 2. 2 6. 4 Cparafiins 1. 3 trace 0.2 0.8 0. 2 01-011 naphthenes 4. 0 2.8 2. 3 3. 22. l 1,3-dimethyl-A 17. 8 24. 6 29. 7 68. 7 70. 1 1,2- and 1,4-dimethyl-No perhydroacenaphthene remained in the reaction mixture by the time thefirst product sample was taken.

In FIG. 2 the values listed in Table II for the contents ofl-ethyladamantane and 1,3-dimethyladamantane have been plotted againstreaction time. Reference to FIG. 2 shows that without free HCll-ethyladamantane quickly formed and that it constituted over one-halfof the reaction product when a one-hour reaction time was reached.However further conversion of this isomer did not then occur and itscontent remained steady at about 56%. A slow formation of the1,3-dirnethyl isomer occurred as shown in Table II but this evidentlywas derived mainly through isomerization of the non-bridgehead dimethylisomers and not l-ethyladamantane. These results show that isomerizationin the absence of free HCl is not a satisfactory way of obtainingbridgehead dimethyladamantane in good yield.

FIG. 2 further shows that when an HCl pressure was applied to thereaction zone, the ethyladamantane isomerized rapidly and the yield of1,3-dimethyladamantane increased sharply. This illustrates theimportance of using free HCl in the reaction zone in practicing-thepresent invention.

Example 2 In this example perhydroacenaphthene was isomerized generallythe same way as in the preceding example except that free HCl was usedinitially in amount equivalent to 10 p.s.i. measured at 0 C. (about 13.3p.s.i. at the reaction temperature). Specifically the bomb contained14.2 g. of the A101 complex, 5.0 g. of uncomplexed AlCl 14.8 g. of amixture of the four perhydroacenaphthene isomers and the free HCl. Thereaction temperature was about 89 C. Compositions of productcorresponding to three reaction times as shown in Table III.

Example 3 A comparative run was made with free HCl under the conditionsdescribed in Example 2 except that the reaction temperature wasmaintained at about 42 C. instead of 89 C. Results are shown in TableIV.

TABLE IV.ISOUERIZATION OF PERHYDROACENAPH- THENE AT 42 0. WITH FREE HClReaction time, min 60 120 180 240 Free 1101 Yes Yes Yes Yes Compositionof Product, wt. percent:

04 paraflins 2.1 2. 8 3.0 2. 6 C parafiins.-. 2.1 2. 8 1. 1. C6parafilns 0.1 0.5 0.6 0. 6 01-011 naphthenes. 1. 8 2. 2 2. 3 1. 81,3-dimethyl-A- 3. 4 14. 8 23. 6 26. 0 1,2- and 1,4-dimethyl-A. 7. 4 4.62.8 2. 1 l-ethyl-A 49. 9 09. 0 65. 2 60. 5 Zethyl-A 33. 4 3. 3 1. 5 3. 9

As in the previous runs no perhydroacenaphthene remained in the productby the time the first sample was taken at one hour.

FIG. 3 shows the 1,3-dimethyladamantane content of the products ofExamples 2 and 3 as a function of reaction time. A comparison of the twocurves shows the importance of reaction temperature in obtaining a highyield of the bridge-head dimethyl isomer within a reasonable reactiontime. This figure considered together with FIG. 2 shows that both anelevated temperature and presence of free HCl, as herein specified, areimportant for achieving the desired results.

When any C or C tricyclic perhydroaromatic is substituted forperhydroacenaphthene, results analogous to those shown in the foregoingexamples are obtained. In the absence of free HCl, or when it is presentbut the -temperature is below the herein specified range, the

reaction tends to stop or be impractically slow at a stage when ethylintermediates predominate. However, when free HCl at a partial pressureas herein specified and a temperature above 55 C. are employed, any Ctricyclic perhydroaromatic can readily be isomerized to1,3,5-trimethyladamantane and any C tricyclic perhydroaromatic canlikewise be converted to 1,3,5,7-tetramethyladamantane.

We claim:

1. Method of preparing polymethyladamantane of the C -C range in whichthe methyl groups are located at bridge-head positions of the adamantanenucleus which comprises contacting a tricyclic perhydroaromatic having12-14 carbon atoms at a temperature in the range of 55-150 C. and in thepresence of free HCl at a partial pressure of at least 0.1 p.s.i. with apre-formed liquid complex obtained by reacting AlCl HCl and a paraflinhydrocarbon having at least seven carbon atoms and continuing saidcontacting under the conditions specified until at least a major portionof the tricyclic perhydroaromatic has been converted to said bridgeheadpolymethyladamantane.

2. Method according to claim 1 wherein said temperature is in the rangeof 70-120 C.

3. Method according to claim 1 wherein the I-ICl partial pressure is atleast 1.0 p.s.i.

4. Method according to claim 1 wherein a C tricyclic perhydroaromatic isused and a major portion thereof is converted to 1,3-dimethyladamantane.

5. Method according to claim 4 wherein said temperature is in the rangeof 70-120 C.

6. Method according to claim 5 wherein the HCl partial pressure is atleast 1.0 p.s.i.

7. Method according to claim 1 wherein a C tricyclic perhydroaromatic isused and a major portion thereof is converted to1,3,S-trimethyladamantane.

8. Method according to claim 7 wherein said temperature is in the rangeof 70-120 C.

9. Method according to claim 8 wherein the HCl partial pressure is atleast 1.0 p.s.i.

10. Method according to claim 1 wherein a C tricyclic perhydroaromaticis used and a major portion thereof is converted tol,3,5,7-tetramethyladamantane.

11. Method according to claim 10 wherein said temperature is in therange of 70-120 C.

12. Method according to claim 11 wherein the HCl partial pressure is atleast 1.0 p.s.i.

13. Method of preparing polymethyladamantanes of the C -C range in whichthe methyl groups are located at bridgehead positions of the adamantanenucleus which comprises contacting a tricyclic perhydroaromatic having12-14 carbon atoms at a temperature in the range of 55-150" C. and inthe presence of free HCl at a partial pressure of at least 0.1 p.s.i.with a pre-formed liquid complex obtained by reacting AlCl HCl andparaffin hydrocarbon having at least seven carbon atoms, continuing saidcontacting under the conditions specified until at least a major portionof the tricyclic perhydroaromatic has been converted topolymethyladamantanes, whereby a minor but substantial proportionthereof have at least one methyl group at a non-bridgehead position,reducing the temperature of the reaction mixture to within the range-ofO50 C. and continuing the contacting at said temperature of O-SO" C.until said proportion has been substantially reduced.

14. Method according to claim 1 wherein the first-mentioned temperaturerange is 70-l20 C. and said partial pressure is at least 1.0 p.s.i.

15. Method of preparing 1,3-dimethyladamantane in high purity whichcomprises contacting a C tricyclic perhydroaromatic at a temperature inthe range of 55- C. and in the presence of free HCl at a partialpressure of at least 0.1 p.s.i. with a pre-formed liquid complexobtaining by reacting AlCl HCl and paraffin hydrocarbon having at leastseven carbon atoms until a major portion of the tricyclicperhydroaromatic has been converted to mixed dimethyladamantanesincluding a minor amount of the 1,2- and 1,4-isomers, reducing thetemperature of the reaction mixture to within the range of 050 C. andcontinuing the contacting at said temperature of 0-50 C. until saidamount has been substantially reduced by isomerization thereof to1,3-dimethyladamantane.

16. Method according to claim 15 wherein the firstmentioned temperaturerange is 70-120" C. and said partial pressure is at least 1.0 p.s.i.

References Cited UNITED STATES PATENTS 4/1964 Schneider 260666 6/1966Schneider 260-666

1. METHOD OF PREPARING POLYMETHYLADAMANTANE OF THE C12-C14 RANGE INWHICH THE METHY GROUPS ARE LOCATED AT BRIDGE-HEAD POSITIONS OF THEADAMANTANE NUCLEUS WHICH COMPRISES CONTACTING A TRICYCLICPERHYDROAROMATIC HAVING 12-14 CARBON ATOMS AT A TEMPERATUREIN THE RANGEOF 55-150*C. AND IN THE PRESENCE OF FREE HCL AT A PARTIAL PRESSURE OF ATLEAST 0.1 P.S.I. WITH A PRE-FORMED LIQUID COMPLEX OBTAINED BY REACTINGALCL3, HCL AND A PARAFFIN HYDROCARBON HAVING AT LEAST SEVEN CARBON ATOMSAND CONTINUING SAID CONTACTING UNDER THE CONDITIONS SPECIFIED UNTIL ATLEAST A MAJOR PORTION OF THE TRICYCLIC PERHYDROAROMATIC HAS BEENCONVERTED TO SAID BRIDGEHEAD POLYMETHYLADAMANTANE.